The one I did was very simple, just 3 boxes really.
I spent 12 hours making the snow shovel, so we could say 10 hours for a more complicated transformer.

I charge $120/hr to do architectural design work for home owners.
$60/hr to do contract work for architects.

So I guess a minimum of $600 up to $1200 per custom made transformer.
With repetition I would gain speed so would need less.
They wont really sell well on the Unity store at $5 each so the patreon money would have to make it worth while.

If only there were transformer nerds, like train nerds.

My Patreon idea is:Tzan is creating Patreon donations!
6. people give me money, because they want to donate but can't be bothered to find creators
7. I find Patreon creators I like and re-donate the money
8. minus a small fee for my service
9. profit!

But making transformers for money sounds cool.
Shit! am I a transformer nerd??